Allow generic SIMD array element type

compiler/rustc_typeck/src/check/check.rs

@@ -1220,6 +1220,7 @@ pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
             match e.kind() {
                 ty::Param(_) => (), // pass struct<T>(T, T, T, T) through, let monomorphization catch errors
                 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok
+                ty::Array(t, _) if matches!(t.kind(), ty::Param(_)) => (), // pass struct<T>([T; N]) through, let monomorphization catch errors
                 ty::Array(t, _clen)
                     if matches!(
                         t.kind(),

src/test/ui/simd/simd-generics.rs

@@ -10,7 +10,15 @@ struct f32x4(f32, f32, f32, f32);
 
 #[repr(simd)]
 #[derive(Copy, Clone)]
-struct S<const N: usize>([f32; N]);
+struct A<const N: usize>([f32; N]);
+
+#[repr(simd)]
+#[derive(Copy, Clone)]
+struct B<T>([T; 4]);
+
+#[repr(simd)]
+#[derive(Copy, Clone)]
+struct C<T, const N: usize>([T; N]);
 
 
 extern "platform-intrinsic" {
@@ -29,7 +37,23 @@ impl ops::Add for f32x4 {
     }
 }
 
-impl ops::Add for S<4> {
+impl ops::Add for A<4> {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        unsafe { simd_add(self, rhs) }
+    }
+}
+
+impl ops::Add for B<f32> {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        unsafe { simd_add(self, rhs) }
+    }
+}
+
+impl ops::Add for C<f32, 4> {
     type Output = Self;
 
     fn add(self, rhs: Self) -> Self {
@@ -39,19 +63,23 @@ impl ops::Add for S<4> {
 
 
 pub fn main() {
-    let lr = f32x4(1.0f32, 2.0f32, 3.0f32, 4.0f32);
+    let x = [1.0f32, 2.0f32, 3.0f32, 4.0f32];
+    let y = [2.0f32, 4.0f32, 6.0f32, 8.0f32];
 
     // lame-o
-    let f32x4(x, y, z, w) = add(lr, lr);
-    assert_eq!(x, 2.0f32);
-    assert_eq!(y, 4.0f32);
-    assert_eq!(z, 6.0f32);
-    assert_eq!(w, 8.0f32);
-
-    let lr2 = S::<4>([1.0f32, 2.0f32, 3.0f32, 4.0f32]);
-    let [x, y, z, w] = add(lr2, lr2).0;
-    assert_eq!(x, 2.0f32);
-    assert_eq!(y, 4.0f32);
-    assert_eq!(z, 6.0f32);
-    assert_eq!(w, 8.0f32);
+    let a = f32x4(1.0f32, 2.0f32, 3.0f32, 4.0f32);
+    let f32x4(a0, a1, a2, a3) = add(a, a);
+    assert_eq!(a0, 2.0f32);
+    assert_eq!(a1, 4.0f32);
+    assert_eq!(a2, 6.0f32);
+    assert_eq!(a3, 8.0f32);
+
+    let a = A(x);
+    assert_eq!(add(a, a).0, y);
+
+    let b = B(x);
+    assert_eq!(add(b, b).0, y);
+
+    let c = C(x);
+    assert_eq!(add(c, c).0, y);
 }

src/test/ui/simd/simd-type-generic-monomorphisation-non-primitive.rs

@@ -0,0 +1,14 @@
+// build-fail
+
+#![feature(repr_simd)]
+
+struct E;
+
+// error-pattern:monomorphising SIMD type `S<E>` with a non-primitive-scalar (integer/float/pointer) element type `E`
+
+#[repr(simd)]
+struct S<T>([T; 4]);
+
+fn main() {
+    let _v: Option<S<E>> = None;
+}

src/test/ui/simd/simd-type-generic-monomorphisation-non-primitive.stderr

@@ -0,0 +1,4 @@
+error: monomorphising SIMD type `S<E>` with a non-primitive-scalar (integer/float/pointer) element type `E`
+
+error: aborting due to previous error
+